Photogrammetry is the science of obtaining accurate information about an object by recording and measuring photographic images of the object. Photogrammetric methods are used for making surveys and maps employing aerial photography, although surface photography may also be employed for this purpose. Normally, however, aerial photography is preferred since it is possible to survey and map large areas with a minimum of time and effort. Photo surveying is particularly useful in the mapping of remote areas where accessibility is limited.
Conventionally, cameras employed in photogrammetric work are of the box type and normally employ larger size sheet film (8".times.10" or 4".times.5"). Such box cameras normally employ ground glass viewers under a hood for insuring proper image focus. In box cameras the lens is usually incorporated into a moveable bellows that slides back and forth on a rail or frame allowing the lens to change focus. Such box cameras, which are called technical or viewing cameras, are expensive, heavy and can be difficult to operate and have been used almost exclusively by professional photographers. However, even for professional photographers, the large box cameras are not ideally suited for out of studio photogrammetric operations, such as aerial photography, surveying and mapping, and other field operations because of their weight and lack of durability.
Ideally, cameras employed for aerial photography, surveying and mapping and other photogrammetric work should be dimensionally stable, lightweight, easily operated for accurate focus and be adapted for use of the larger sheet film. Photogrammetry, however, is not limited to the science of surveying or aerial mapping, but has great potential in many types of dimensional control work.
A highly successful photogrammetric box camera is described and claimed in U.S. Pat. No. 4,835,559 granted May 30, 1989 to Mark Hattan. This camera has proven successful for aerial photo surveying where most of the images are at infinity. However, a lightweight dimensionally stable camera finds use in many other fields and even for studio applications where simplicity of operation and ruggedness is needed in a camera to achieve essentially distortion-free images. Accordingly, the lens mount of the camera described in U.S. Pat. No. 4,835,559 has limited forward and rear movement for changing the fixed focus of the camera from infinity to closer distances. A close-up lens can be attached to the main lens for close photography. In another embodiment of the camera described in U.S. Pat. No. 4,835,559, an inner body which carries the lens is movably mounted in the camera housing for telescopic movement within the camera housing to provide variable focusing. A rack and pinion gear assembly is provided for moving the inner body and lens for focusing. However there is no provision in the camera design for altering the depth of field, and minor depth of field adjustment must be supplied with the lens mechanism by opening or closing the lens aperture.
As described in U.S. Pat. No. 4,835,559, the camera components including the camera housing, lens mount and inner body are formed of a dimensionally stable material comprising multiple layers of resin impregnated graphite fabric applied over a core form followed by heating the core and fabric in a mold to cure the resin. This method lends itself to the production of simple shapes, such as the camera housing. However, forming more intricate shapes using this method of production is time consuming and expensive. For example, in U.S. Pat. No. 4,835,559, the cost of the camera housing is substantially increased because the film holder adapter, which is formed integrally with the camera housing and comprises the rear face of the camera housing, is a more complex shape adapted for receiving a film holder.